Liquid crystal properties of metal–salicylaldimine complexes.: Chemical modifications towards lower symmetry

Helical supramolecular organizations from metal-organic liquid crystals

Pyrimidine Ring as Building Block for the Synthesis of Functionalized π-Conjugated Materials

The preparation of optically active poly(isocyanide)s derived from chiral promesogenic monomers is reported. Remarkably, the stereogenic carbon atom in the monomer is able to pass its chiral “information” to the growing polymer backbone which is at least 14 atoms (approximately 16 A) remote from it. The sense of helical induction in these conformationally rigid polymers is compared to the helical sense of the cholesteric phases, as well as to the helical senses of chiral smectic C phases, induced by the monomers in nematic and smectic C phases, respectively. Both relate to the odd−even rules for chiral sense changes in liquid crystalline phases. The role of noncovalent interactions in the polymerization has been proven by performing the reactions at various concentrations and in different solventsthe chiral induction from monomer to polymer is greatest in most concentrated reactions and in solvents with a balance between high dipolarity−polarizability and low hydrogen bond accepting and cavitational terms...

Long-Range Chiral Induction in Chemical Systems with Helical Organization. Promesogenic Monomers in the Formation of Poly(isocyanide)s and in the Organization of Liquid Crystals

A series of liquid crystals have been synthesized and studied based upon mononuclear ortho-platinated rod-like heteroaromatic and 1,3-diketonate ligands. The liquid crystalline properties of these molecules were investigated using polarized light optical microscopy, differential scanning calorimetry, single crystal X-ray diffraction, and powder X-ray diffraction. Increasing the number of alkyl chains attached to the 1,3-diketonate units resulted in a transition from lamellar (SmA) to hexagonal columnar phases (Colh). The 2-thienylpyridine units were previously unexplored in metallomesogenic complexes and these studies extend the utility of ortho-platinated 2-phenylpyridines and 2-thienylpyridines to produce columnar liquid crystalline phases. The platinum complexes all display photoluminescence and are of interest for electrooptical applications.

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Columnar mesophases from half-discoid platinum cyclometalated metallomesogens

A study has been undertaken of the structure-activity relationship of eight new chiral compounds having either a pyrazole (series P) or an isoxazole (series I) ring as a central bridge in the mesogenic core. The presence of dimers in the pyrazole compounds accounts for their lower P s values in comparison with the isoxazole analogues. The corresponding four beta-diketone precursors have also been studied and these, as expected given their bent molecular shape, show much worse mesomorphic and ferroelectric behaviour. In order to complete the study, the molecular dipoles of the three types of derivative have been determined using AM1 calculations. Two types of chiral tail have been incorporated into the compounds: alkoxy and alkanoyloxy. The latter tail gives rise to the best mesomorphic and ferroelectric properties. A study of the tail conformations by MM2 calculations provides an explanation of these results. The highest P s value (137 nC cm) has been obtained for the isoxazole derivative with the (2S)-2-...

FLCs with a five-membered ring in the mesogenic core

Chiral oxovanadium(IV), copper(II) and palladium(II) beta-diketonates show a room temperature tilted columnar mesophase (rectangular P21). The dielectric response of these compounds was measured in the frequency range 10-2-109Hz. Three different relaxation processes have been observed in the columnar phase. One of them is only present in this mesophase and we suggest that it is a Goldstone-like mode, similar to the one present in the helical SmC* phases. In our case the presence of the helix was confirmed by circular dichroism studies.

Dielectric study of the tilted columnar mesophase in three new chiral metallorganic discotic mesogens

A new series of four mononuclear orthopalladated complexes which contain a Schiff base and an aliphatic β-diketone as ligands is described. The miscibility of the modified complexes in a standard organic host material is improved in comparison with complexes studied previously. The increased solubility of the complexes leads to ferroelectric organometallic–organic mixtures with lower viscosities and switching times than purely organometallic mixtures, while the spontaneous polarization (Ps) values are maintained or increased.

Raquel Iglesias

Papers

FLCs with a five-membered ring in the mesogenic core

Dielectric study of the tilted columnar mesophase in three new chiral metallorganic discotic mesogens

Influence of the host–guest interactions on the ferroelectric properties of mononuclear orthopalladated metallomesogen mixtures

Dielectric relaxation processes in a brick‐like metallomesogen ferroelectric liquid crystal